RegCM4.6两种积云参数化方案在东亚模拟结果的评估

新一代区域气候模式RegCM4.6引进了Mix积云参数化方案,可以将之前版本中的Emanuel和Grell方案结合在一起,以弥补单个参数化方案的不足。利用2016年MODIS(Moderate-resolution imaging spectroradiometer)数据对RegCM4.6中Mix和Emanuel积云参数化方案模拟的东亚云量(Cloud fraction,CF)、冰水柱含量(Ice water path,IWP)和液水柱含量(Liquid water path,LWP)进行初步评估,计算了相关系数(r)、平均绝对误差(Mean absolute error,MAE)、平均偏差(Mean bias error,MBE)和均方根误差(Root mean square error,RMSE),以便为相关研究选取积云参数化方案提供参考依据。结果表明：(1)模拟的CF的MBE大致以胡焕庸线为界,西北部为轻微高估,东南部通常为低估。2种方案在夏季的模拟效果最好,冬季最差。Mix方案的MAE、MBE和RMSE的绝对值在四季普遍小于Emanuel方案。(2)模式明显低估了东亚的IWP,...     

Coherency matrix-based proper orthogonal decomposition with application to wind field simulation

Proper Orthogonal Decomposition （POD） provides a powerful modal transformation tool for stochastic dynamics. In this paper, coherency matrix-based proper orthogonal decomposition （CPOD） is presented as an innovative form of the POD based on cross power spectral density matrices. By introducing a discretizing scheme, the CPOD-based spectral representation method is obtained for use in stochastic simulation. Moreover, some criteria are proposed that allow the truncation order of CPOD to be conveniently determined. A numerical example to illustrate the application of the proposed method for the simulation of a wind velocity field is provided.     

气体吸附对煤层安全钻井液密度的影响

煤岩中割理极为发育,导致煤层非均质性极强,在煤层钻井过程中井壁极易垮塌,掩埋钻具,钻井过程中配置合理的钻井液用以保持井壁稳定具有重要的意义。现阶段主要是运用经典连续介质理论模型进行钻井过程中安全钻井液密度窗口预测,导致现场实际效果较差。实际煤层不仅割理发育并且大量CH₄以吸附态赋存于煤层中,将弱化煤岩力学强度,使原本就易失稳的井壁越加不稳定。因此,针对煤层为非连续介质的特殊性,基于非连续介质力学构建的离散元模型分析钻井过程中煤层井壁稳定性,并结合连续介质强度分析法在考虑气体吸附对煤岩力学强度弱化影响的情况下,用以确定煤层最佳防塌钻井液。最后,根据山西省宁武盆地的煤岩数据及现场钻井液资料,利用上述理论进行实例计算,指出研究区煤层防塌需保证钻井液密度大于1.009 g/cm3,并且需在钻井液中添加暂堵剂以提高其封堵能力。